Rock-drill of the percussion type.



No. 808,377. PATBNTED DEC. 26, 1905, W. O. JOHNSON & G. G. PEARSON. ROCK DRILL OF THE PERCUSSION TYPE.

APPLICATION FILED AUG. 26, 1904.

nn'rrnn s'rErEs PATENT OFFIOE.

WVALTER CLAUDE JOHNSON AND GEORGE CHARLES PEARSON, OF OLD CHARLTON, ENGLAND.

Specification of Letters Patent.

Patented. Dec. 26, 1905.

Application filed August 26, 1904. Serial No. 222,212-

Zo coZZ whont it may concern:

Be it known that we, WALTER CLAUDE JOHNSON and GEoRcE CHARLES PEARSON, subjects of the King of Great Britain, and residents of Old Charlton, England, have invented certain new and useful Improvements in Rock-Drills of the Percussion Type, of which the following is a specification.

Our invention relates to improvements in rock-drills of the percussion type by means ofwhich certain advantages are obtained.

In carrying our invention intoeffect we employ a cylinder and piston as in other forms of rock-drills driven by compressed air; but instead of supplying compressed air in the usual manner to the cylinder we compress the air in the cylinder itself and use the air so compressed to drive forward the piston in its working stroke.

In one convenient way of carrying our invention into effect we continue the pistonrod' or its equivalent back through the cylinder-cover to a cross-head upon which are mounted two rollers. These rollers are acted upon by two snails or cams mounted on a shaft parallel to the cross-head in such man ner that the rotation of the said snails or cams presses the cross-head, and with it the piston, backward, so as to compress air between'the back of the piston and the cylinder-cover. When the noses of the snails have assed the rollers, the cross-head is released and the air compressed behind the piston drives the latter forward and with it the drill connected therewith. The cam-shaft may be driven in any convenient known way and may be fitted with a fly-wheel and balance-weights and with the usual slipping mechanism and reduction-gear. The drillmandrel may be connected with the piston and be fed and rotated in any of the wellknown ways. Air may be drawn into the forward end of the cylinder during the compression-stroke through a non-return valve or the like, and this air may act as a cushion for the piston at the forward end of its working stroke. A portion of this air may be passed through a by-pass fitted with a dischargevalve to the back of the piston, so as to make up for any air which may have leaked from the compression-chamber. The air may be filtered in any known manner. The cylinder may be kept cool by means of a waterjacket, and this water after passing through the water-jacket may be employed for washing out the drill-hole. In another form the cross-head may be actuated by means of an endless chain, which may have projecting lugs at intervals to engage lugs on the crosshead.

We shall now proceed to describe a preferred form of our invention, and for that purpose we shall refer to the accompanying drawings, of which Figure I is a vertical longitudinal section; Fig. II, a plan. Fig. III is a cross-section on line 3 3 of Fig. I; Fig. IV, a part longitudinal section illustrating the actuation of the crosshead by means of an endless chain.

Referring now to the figures, 1 is the drillmandrel, 2 the cylinder, and 3 the piston which as it moves to and fro in the cylinder carries the reciprocating mandrel with it. The said mandrel is prolonged through the back of the cylinder and through the crosshead 4, upon which are mounted two rollers 5. These rollers are acted upon by two snails or cams 6, mounted on the power-driven shaft 7. When shaft 7 is rotated in the direction of the arrow shown in Fig. I, the cams pull the mandrel and piston backward, so that the air is compressed in the back part 8 of the cylinder. As soon as the noses of the cam 6 have disengaged themselves from the rollers 5 the compressed air at the back of the cylinder drives the piston forward, causing the drill to strike a blow on the rock or other material acted upon. On so being driven forward the air in the fore part of the cylinder escapes through the port 9, hereinafter referred to, until this port has reached the front part of the cylinder, so as to be closed, whereupon on the further movement forward of the piston some air is driven through the non-return valve 10 and by-pass 11 to the rear end 8' of the cylinder. When the piston has advanced sufficiently to cover the entrance to valve 10, a cushioning effect is obtained at the fore end of the cylinder. When the cams again encounter the rollers 5, the mandrel is moved backward, and when the port 9 is free of the front of the cylinder air is thereby admitted, as will be hereinafter mentioned, to the front part of the cylinder,

therein for the purpose of again. propelling the mandrel forward. To obtain the necessary elasticity and some slip, so as to avoid unnecessary shock to the parts and loss of power through friction of the mandrel in the piston, instead of mounting the latter di rectly on the mandrel we mount it loosely 011 the sleeve 12, which embraces the said mandrel and which lies between two sets of springs 13 and 14, surrounding the mandrel, as shown. The port 9 hereinbefore referred to, is cut in the sleeeve 12 and communicates with a channel or flat 15 on the mandrel, so as to constitute a suitable nonreturn valve. The ratchet-nut or equivalent device for rotating the mandrel is positioned at 16; but this forms no part of our invention.

A coil-spring 1 is interposed between the cross-head 4 and the rear end of the mandrel. The tension of the spring 4 is such that it will not interfere with the rear movement of the mandrel owing to the engagement of the cams with the cross-head. Should the drill, however, not be held close enough to the work, the cross-head 4 may abut against the cams when they are assuming a position to contact therewith. Should this be the case, the interposition of the spring 1 between the end of the mandrel and the cross-head will prevent said cross-head from striking the cams hard enough to damage any of the parts.

In Fig. IV we illustrate the modified method of actuating the cross-head by means of an endless chain and projecting lugs hereinbefore referred to. In this figure, 17 17 are two shafts over which passes an endless chain 18. Upon this chain are lugs or studs 19, which engage with the crosshead or with lugs 20 thereon. It will be seen that when a lug on the chain engages with the cross-head the mandrel 1 is actuated in the same manner as when a cam or snail 6 engages with the rollers 5 in the previously-described form.

Having thus described our invention, what we claim as new, and desire to secure byLetters Patent, is

1. In a drill, a cylinder, a piston therein, a working tool associated with said piston, means for moving the piston to the rear end of the cylinder to compress a charge of air therein and releasing the same to permit it to move forward under the expansion of the air compressed on the rearward stroke, and means for causing the air in the cylinder in advance of the piston during the forward movement thereof to successively pass into the atmosphere, to pass to the cylinder in.

rear of the piston, and to form a cushion for said piston.

2. In a drill, a cylinder, a piston therein, a working tool associated with said piston, means for moving the piston rearwardly to compress a charge of air in the rear end of the cylinder and releasing the same to permit it to move forward under the expansion of the air compressed on the rearward stroke, said cylinder having a port connecting the front and rear ends thereof, the inlet end of said port being so positioned as to be cut off by the piston during its forward movement.

3. In a drill, a cylinder, a piston-rod, a piston thereon, a working tool associated with said piston-rod, means for moving the piston rearwardly to compress a charge of air and for releasing the same to permit it to move forward under the expansion of air compressed on the rearward stroke, said pistonrod having a port therein normally connecting the forward portion of the cylinder with the atmosphere and adapted to be closed during a portion of the forward movement of said piston.

4. In a drill, a cylinder, a mandrel extend ing therethrough, a piston yieldably connected to said mandrel, and means for moving the piston in one direction to compress a charge of air in the cylinder and releasing the same to permit it to move in the opposite direction under the expansion of the air compressed.

5. In a drill, a cylinder, a mandrel extending therethrough, a sleeve loosely mounted on said mandrel, a piston secured to said sleeve and working within said cylinder, springs interposed between the ends of the sleeve and abutments on the mandrel, and means for moving the piston in one direction to compress a charge of air in the cylinder and releasing the same to permit it to move in the opposite direction under the expansion of the compressed air.

In witness whereof we have hereunto set our hands in presence of two witnesses.

WALTER CLAUDE JOHNSON. GEORGE CHARLES PEARSON.

Witnesses to the signature of Walter Claude Johnson:

WARREN BAXTER, ALLAN BAXTER.

Vitnesses to the signature of George Charles Pearson:

WALTER W. REDMAN, ARTHUR H. PAUL. 

